In catalytic converters, a substrate is coated with a catalyst washcoat which contains the catalyst(s), catalyst supports, etc. High surface area is desirable in the washcoat to maximize catalysis. Other desirable washcoat properties include thermal stability and a pore size distribution that allows high flow-through of gases to optimize contact with the catalysts). In particular, use of fine particles in the washcoat can result in a dense washcoat layer with reduced porosity and impaired catalytic activity. In addition, dense nonporous washcoats may crack during heat treatment resulting in lack of adhesion and compromised durability.
There exists a need for catalyst washcoats with increased porosity, particularly catalyst washcoats that can be produced using simple methods that are easily incorporated into the manufacture of catalyst articles such as catalytic converters. The present invention addresses these needs.